Siemens SINAUT ST7 System Manual page 218

Installing and putting a SINAUT modem into operation
5.5 MD2 dedicated line modem
NTP = number of tapping points
*) not permitted with postal leased lines. Transmit level must be set to –9 dB.
The values in the table are guidelines.
When calculating the maximum range, a power margin of 4 dB was included. This is to
compensate for fluctuations in cable properties that experience has shown to occur in
practise, and thus always ensure that sufficient signal level is available for problem-free data
transmission. To calculate the values shown in the table, the following formula was used:
S
m ax
A
Insert
A
Cable
A
LTOP
NTP
N
min
N
Send
N
Res
S
max
Sample calculation:
For core diameter 0.8 mm, at 2400 bps, with LTOPs and transmit level –6 dB
S
m ax
S
m ax
S
m ax
Using the above formula, users can create their own calculations if the data of the cable
being used is known.
For lines leased from the telephone company, the range calculation is unnecessary. Here,
the public telephone company is responsible for an adequate signal level. Recommended
cable quality for lines leased from a telephone company:
Analog connections of the type M.1020 or M.1025 in the landline network.
218
[ ]
+ − −
N N N
= m in
Send Res
A
Cable
Insertion loss per tapping point [in dB]
Attenuation per km of the cable used [in dB]
Attenuation per LTOP [in dB]
Number of tapping points
Minimum receive level [in dB]
(-43 dB for MD2, please use only absolute value in formula)
Transmit level [in dB]
(normally –6 dB or 0 dB)
Power margin [in dB]
Max. range [in km]
[ ]
− 43 + ( − ) 6 − 4 − 2 × 0
=
1 4 ,
43 − 6 − 4 − 0 4 ,
= − ×
NTP
1 4 ,
32 6 , 0 6 ,
= − ×
NTP
1 4 , 1 4 ,
2 ×
A
A
− × Insert
LTOP
NTP
2 , 0 2 , + 2 × 0 2 ,
− ×
NTP
1 4 ,
0 2 , + 0 4 ,
1 4 ,
= 23,2 − ×
S NTP
m ax
+ 2 ×
A
LTOP
A
Cable
0 5 ,
System Manual, 07/2009, C79000-G8976-C178-07
Station control system